1. Field of the Invention
The present invention relates to a unique time generating device incorporated in a computer which permits communication between a plurality of computers based on a common time concept, and also to an authenticating device using the unique time generating device to allow the computers to authenticate each other without errors.
2. Description of the Related Art
An atomic clock (cesium clock) is known at present as the most accurate time measuring device, which is accurate to one part in 10.sup.8 sec. Specifically, such an atomic clock defines, as one second, the duration of the natural resonance frequency of the cesium atom (9,192,631,770), and International Atomic Time is determined by the Bureau International de l'Heure (on the premises of the Paris Astronomical Observatory) by averaging the measured values of atomic clocks located throughout the world. The value of the second is thus managed today in accordance with the internationally determined atomic time, whereas the length of the day is managed in accordance with Universal Time. According to Universal Time, the hours of the day are numbered from 0 to 24, using as 0:00 p.m. (noon) a time point when the sun crosses the Prime Meridian of longitude passing through the old Greenwich Observatory, England (southing time) and using as 0:00 a.m. (midnight) a time point 12 hours before and after the southing time. The local standard time in each individual country of the world is set on the basis of a predetermined longitude passing through the country, and it is determined how many hours the local standard time is ahead or behind Universal time (Greenwich Mean Time). Specifically, Japan standard time is set, using as 0:00 p.m. a time point or southing time when the sun crosses Akashi Observatory (the 135th degree of east longitude). Further, in a large majority of the countries of the world, the Gregorian calendar is still used, in accordance with which each common year is set to have 365 days while every fourth year is set as a leap year having a total of 366 days. The Gregorian calendar was introduced on the basis of the fact that one revolution period of the earth relative to the sun (one solar year) is 365.2422 days, and it defines one year using its approximate value of 365.2425 days as one solar year.
However, the setting of the year and day based on the astronomical periods (such as the periods of the earth's revolution around the sun and rotation on its own axis) is not satisfactory, because the length of the day is somewhat changing due to the fact that the speed of the earth's rotation on its axis is not always constant by being influenced by fluctuations of the earth's axis and seasonal variations. In addition, because the speed of the earth's rotation on its axis has a tendency to slow down little by little, a slight difference arises between International Atomic Time constantly measured by the atomic clocks and Universal Time measured on the basis of the movements of heavenly bodies. This difference between the two times is currently compensated for by adding or removing one second (leap second) to or from the last minute on June 30 or December 31 in the year when it has exceeded 0.9 second.
The time management on the earth today is conducted using the date and hour day and time concept based on such Universal time, International Atomic Time and Gregorian calendar, and various equipment existing on the earth, such as computer-containing control equipment involving accurate timing control, contains a timer circuit (such as a quartz oscillator circuit), to which the current time (Universal Time) is input so as to perform timewise drive control of the equipment on the basis of time indicated by the timer circuit. That is, in general commercially available computers and memory-contained timekeepers, calendar data for 100 years to come (corresponding to the life of the equipment) are prestored so that a current time is sequentially displayed through timer operation of a quartz oscillator circuit according to the prestored calendar data. Such time set on the basis of Greenwich Mean Time is, so to speak, "artificially set time" based on astronomical occurrences, such as the earth's revolution around the sun and rotation on its own axis, which lasts from the beginning of the universe to the future to constantly indicate a changing current time of, e.g., 11:20'22" a.m., Jan. 20, 1996 as shown in FIG. 26.
In recent years, however, it has become necessary to remotely operate various control equipment loaded in a spacecraft operating off the earth's time space (such as a weather satellite moving around the earth or an interplanetary probe satellite), and to connect, in a network, computers located in various countries of the world so as to allow the computers to access information at predetermined timing. If, in such applications, time to be used in common between the computers is to be set on the basis of Universal Time or the local standard time of a specific country, a leap second occurring once in some years must be considered and proper access may not be guaranteed because it is unclear whether there exists a same time standard with another party's computer (e.g., whether a specific party's computer indicates the same time as the other party's computer). In view of this inconvenience, a variety of approaches have been proposed (e.g., in Japanese Patent Laid-open publication No. HEI 4-337943) to smooth the necessary time management, but they could not provide a satisfactory solution to the problem. Further, in the case of a spacecraft flying away from the earth to a far remote planet (such as the "Voyager" rocket searching Saturn), variations in gravitational field would cause "slowing of clocks" as referred to in Einstein's general theory of relativity even though a high-accuracy atomic clock is loaded in the spacecraft's computer. Namely, in a gravitational field far from the earth, electrons move more slowly and hence the frequency of radiated light becomes lower, so that the atomic clock measuring the frequency of light radiated from an atom (cesium atom) is unable to measure time accurately.